CC

/**
 * This class represents a credit card number
 * with methods for validation.
 *
 * @author Lykos
 * @version 11.28.2012
 */
public class CreditCard
{
    private String cardNumber;

    /**
     * Constructor for objects of class CreditCard.
     *
     * @param  cardNumber   A credit card number used to initialize the field
     *
     */
    public CreditCard(String cardNumber)
    {
        this.cardNumber = cardNumber;

    }

    /**
     * Accessor method to return the cardNumber
     *
     * @return  A string that is the credit card number
     */
    public String getCardNumber()
    {
        return cardNumber;
    }

    /**
     * Mutator method to set the cardNumber
     *
     * @param  cardNumber   A credit card number
     */
    public void setCardNumber(String cardNumber)
    {

        this.cardNumber = cardNumber;

    }

    /**
     * Using the leading digits and the length of the card number, this method
     * determines if the card type is either "Visa", "MasterCard", "American Express", or "Discover"
     * or an unknown card type.
     *
     * @return  The credit card type, either "Visa", "MasterCard", "American Express", or "Discover"
     *          or the string "Unknown" if the type cannot be found.
     *
     */
    public String creditCardType()
    {
        //buttload of if statements?
        String cardType = "Unknown";
        if(cardNumber.startsWith("4"))
        {
            if(cardNumber.length() == 13 || cardNumber.length() == 16)
            {
                cardType = "Visa";
            }
        }
        if(cardNumber.startsWith("51") || cardNumber.startsWith("52") || cardNumber.startsWith("53") || cardNumber.startsWith("54") || cardNumber.startsWith("55"))
        {
            if(cardNumber.length() == 16)
            {
                cardType = "MasterCard";
            }
        }
        if(cardNumber.startsWith("34") || cardNumber.startsWith("37"))
        {
            if(cardNumber.length() == 15)
            {
                cardType = "American Express";
            }
        }
        if(cardNumber.startsWith("6011"))
        {
            if(cardNumber.length() == 16)
            {
                cardType = "Discover";
            }
        }

        return cardType;
    }

    /**
     * Determins whether the number parameter is a single or double digit number.
     * If it is a single digit number, return that number, otherwise
     * return the sum of the two digits in the number parameter
     *
     * @param number  A single or double digit integer
     * @return        An integer, either the single digit number parameter
     *                or the sum of the two digits of the double digit parameter
     */
    public int getDigit(int number)
    {
        if(number < 10) {
            return number;
        }
        else {
            if(number == 10) {
                number = 1;
            }
            if(number == 12) {
                number = 3;
            }
            if(number == 14) {
                number = 5;
            }
            if(number == 16) {
                number = 7;
            }
            if(number == 18) {
                number = 9;
            }
            return number;
        }
    }

    /**
     * This method returns the total of doubling every second digit from right to left.
     * If doubling of a digit results in a two-digit
     * number, add up the two digit to get a single digit number and add to the total.
     *
     * @return  An integer which is the sum of the digits.
     */
    public int sumEverySecondDigitRightToLeft()
    {
        int sum = 0;
        for(int index = 1; index < cardNumber.length(); index += 2)
        {
            int digit = Integer.parseInt(cardNumber.substring(cardNumber.length() - (index + 1), cardNumber.length() - index));
            digit = digit * 2;
            digit = getDigit(digit);
            sum += digit;
        }

        return sum;
    }

    /**
     * The method calculates the sum of the digits in the odd positions of the
     * credit card string, going from right to left, where the last number
     * in the credit card string is counted as the first position.
     *
     * @return  An integer which is the sum of the digits.
     */
    public int sumOfOddPlaceDigitsRightToLeft()
    {
        int sum = 0;
        for(int index = 0; index < cardNumber.length(); index += 2)
        {
            int digit = Integer.parseInt(cardNumber.substring(cardNumber.length() - (index + 1), cardNumber.length() - index));
            sum += digit;
        }
        return sum;
    }

    /**
     * The method determines if the credit card number is valid.
     * If the card is valid, the total of sumEverySecondDigitRightToLeft()
     * and sumOfOddPlaceDigitsRightToLeft()
     * should be divisible by 10 with no remainder.
     *
     * @return  A boolean value of true if the card number is valid,
     *          false, otherwise.
     */
    public boolean isValid()
    {

        if((sumEverySecondDigitRightToLeft() + sumOfOddPlaceDigitsRightToLeft()) % 10 == 0)
        {
            return true;
        }
        else
        {
            return false;
        }


    }

}